Manufacture of naphthenic type lubricating oils

ABSTRACT

A process for making naphthenic type lubricating oils from a low VI waxy crude which comprises distilling said low VI waxy crude to 500° to 650° F. at atmospheric pressure to separate distillable fractions therefrom, subjecting the residue to a vacuum distillation at about 25 to about 125 mm Hg absolute pressure to obtain one or more gas oil fractions, optionally hydrotreating said gas oil fractions in the presence of a Ni/Mo catalyst at 550° to 650° F., 0.25 to 1.0 LHSV, and 700-1500 psig, and catalytically dewaxing said distillates in the presence of a H +  form mordenite catalyst containing a Group VI or Group VIII metal at 550° to 750° F., 500 to 1500 psig and 0.25 to 5.0 LHSV, to obtain said naphthenic type oils having pour points of from about -60° to +20° F.

Naphthenic lubricating oils are conventionally made from grade A orcoastal, wax-free crudes by simple distillation of the crude in thepresence of caustic. Due to such simple processing they have beenrelatively inexpensive.

Naphthenic oils have naturally low pour points of from -50° F. in lowviscosity grades to +20° F. in high viscosity grades. Their viscosityIndex (VI) is poor, but, in many applications, this quality is secondaryto cost considerations. There are also some applications where theparticular properties of naphthenic lubes (very low pour point andrelatively high content of aromatic compounds) make them desirable inspite of any price advantage.

Solvent lubricating oils are made from waxy crudes. They require acomplicated refining scheme and are, therefore, more expensive. VI ishigh and pour points of finished oils (after dewaxing) run 0 to +10° F.These lubes must be manufactured from selected waxy crudes, i.e., thosewith VI high enough to give at least 90-95 VI levels in the finishedoils. Waxy crudes with lower VI potential are rejected for solvent lubemanufacture and utilized only for fuels.

This invention is directed to a process for manufacturing relativelyinexpensive naphthenic type lubes from the low VI waxy crudes unsuitablefor solvent lubes and now used for gasoline and fuels. Such a process isdesirable because reserves of grade A or coastal crudes are seriouslydeclining and no new fields of these grades have been discovered. Thus,the process of this invention will permit crudes now going to fuels tofill this gap while saving high VI solvent lube crudes for applicationswhere their special qualities are required.

In essence, the process of the invention involves the steps ofdistilling a low VI waxy crude at atmospheric pressure up to atemperature of about 650° F. to remove the distillable fractiontherefrom, vacuum distilling the residue to obtain gas oil fractions andcatalytically dewaxing the gas oil fractions having an SUS at 100° F.viscosity of from about 60 to about 2000 to obtain the naphthenic typelubricating oil product. Optionally, prior to the catalytic dewaxingstep the gas oil fractions may be hydrogenated if it is desired toimprove color and/or remove nitrogen and sulfur compounds which isdesirable for enhanced product quality or to avoid the adverse effectsof sulfur and nitrogen on the dewaxing catalyst.

Reference is now made to the drawing where the process of the inventionis illustrated in more detail. The crude is first taken through line 11to a still 12 and distilled at atmospheric pressure up to a temperatureof about 650° F. and distillates are sent to fuels manufacture as shownby lines 13, 14 and 15. The residual crude is taken through line 16 tostill 17 and vacuum distilled at about 25 to about 125 mm of mercurypressure (absolute) to give several gas oils of desired viscosities. Theatmospheric and vacuum distillation columns may include causticscrubbing zones to remove undesirable acids in the crude. The vacuum gasoils may next be taken through appropriate lines, shown in the FIGURE aslines 18 to 22 to an optional hydrotreater 23 and hydrotreated toimprove color and remove nitrogen and sulfur compounds. Whether or nothydrotreating will be used depends on the properties of the specificcrudes used along with the desired end uses for the finished lubes. Ifused, the operating conditions for the hydrotreating step are:

Temperature, °F.: 550°-650°

H₂ pressure, Psig: 700-1500

LHSV: 0.25-1.0

Catalyst: Commercially available Ni-Mo

Finally, the distillates are taken through lines 24 to 28 to a dewaxer29 where they are catalytically dewaxed to meet pour pointspecifications. This is accomplished by mixing the oil with hydrogen andcontacting it with a catalyst at elevated temperature and pressure.Normal paraffins and nearly normal paraffins are preferentially crackedto gases and low boiling liquids which may be removed by distillation(not shown). Operating conditions are:

Temperature, °F.: 500°-750°

H₂ pressure, Psig: 500-1500

LHSV: 0.25-5.0

H₂ recycle, SCF/bbl: 1,000-10,000

The catalyst used is an alumino-silicate of the mordenite class. It mustbe decationized, that is Na+ ions replaced with H+ ions, to be activefor this application. A commercially available example of H+ mordeniteis Norton Company's Zeolon H. A group VI or VIII metal such as platinumor palladium is added to the hydrogen mordenite to give the finalcatalyst. In an alternate catalyst, sulfur also may be added to the H+mordenite by using a sulfuric acid treatment before adding the group VIor VIII metal. The sulfur addition is readily accomplished by slurryingH+ mordenite with H₂ SO₄ at 90° C. for 5 hours. After filtration toremove excess H₂ SO₄ liquid, the acid laden mordenite is heated in aprogrammed manner to 480° C. to volatilize acid. Final catalyst containsat least 0.05 wt. % sulfur and more typically 2-4 wt. %.

The catalytic dewaxing operation is preferably carried out in a fixedbed, trickle flow reactor. High pressure and low pressure separatorsremove hydrogen and hydrocarbon gases from the effluent. A vacuumstripper removes products of hydrocracking boiling lower than the feed.Severity is adjusted to meet the spedific pour point target of eachdistillate.

Catalytic dewaxing severity would be adjusted to give the following pourpoints for the particular viscosity grades from the vacuum distillation:

    ______________________________________                                        Viscosity Grade Dewaxed Pour Point                                            (SUS @ 100° F.)                                                                        (F.°)                                                  ______________________________________                                         60             -50                                                           100             -40                                                           500             -10                                                           2000            +10                                                           ______________________________________                                    

A specific example of the type of crude for which this invention isuseful is Nigerian Medium. Nigerian Medium may be contrasted withnaphthenic crude and high VI waxy crude as follows:

    ______________________________________                                                   Amelia A/          Zarzaitine                                                 Perkins A                                                                             Nigerian   (Typical High                                              (Typical                                                                              Medium     VI Waxy Sol-                                               Naphthenic                                                                            (Low VI    vent Lube                                                  Crude)  Waxy Crude)                                                                              Crude)                                          ______________________________________                                        Crude Properties                                                              °API  24.0      26.1        42                                         WT. % wax     0.3       3.0       4.0-5.0                                     650-1070° F. Fraction                                                  Vol. % crude 36        34         22.5                                        WT. % wax    .4-.5      8         13-15                                       Dewaxed satu-                                                                 rates VI     20-40     75         104                                         ______________________________________                                    

Nigerian Medium lacks the VI potential to make a 95 VI solvent lube, butit contains wax and, thus, conventionally would only be used for fuelmanufacture. By using the process of this invention, an inexpensive lubeof intermediate VI quality may be manufactured from Nigerian Mediumcrude. Other useful crudes include Trinidad Light, Garden Island Bay andLake Washington (Louisiana Crudes), Thompson, Webster and Hawkins (TexasCrudes), which crudes contain wax and cannot by prior art methods yield90 VI solvent lubes.

In order to further illustrate the invention the following examples aregiven:

EXAMPLE 1

A sample of Nigerian Medium crude was distilled in a commercialatmospheric distillation unit containing a caustic scrubbing zone togive the following streams:

    ______________________________________                                                       Approx.                                                        Stream         B. Pt. (°F.)                                                                      Vol. % on Crude                                     ______________________________________                                        Wet gas        To 250°                                                                           6.0                                                 Straight run gasoline                                                         Naphtha        250°-420°                                                                  8.0                                                 Atmospheric gas oil                                                                          420°-520°                                                                  22.0                                                Residue        520°+                                                                             64.0                                                ______________________________________                                    

The residue was then distilled in a commercial vacuum distillation unitalso containing a caustic scrubber at 25 to 120 mm of mercury pressure(absolute) to give the streams shown in Table I.

                  TABLE I                                                         ______________________________________                                              Vol %   D1160          VIS   Ppm                                        Stream                                                                              of      Distill, °F.                                                                          SUS/  Sul- Pour D-1500                           No.   Crude   10%    90%  °API                                                                        100° F.                                                                      fur  Pt.  Color                          ______________________________________                                        1     13.0    --     --   --   --    --   --   --                             2      3.5    578     707 23.9  64   2000 +12  1.0                            3     11.0    608     787 22.8  124  1700 +44   1.75                          4      5.0    704     871 20.7  560  2400 +71   2.75                          5     11.0    773     956 18.9 2000  2400 +88  4.0                            6      5.0    813    1064 18.1 5000  3200 +94  6.5                            Caustic                                                                              2.0    --     --   --   --    --   --   --                             Sludge                                                                        Vac-  13.5    --     --   --   --    --   --   --                             Resi-                                                                         due                                                                           ______________________________________                                    

Streams 2 through 6 were then hydrotreated using a commerciallyavailable Ni-MO catalyst (American Cyanamid HDS-9 Trilobe). Thehydrotreating was conducted at a reactor temperature of 650° F.,hydrogen pressure of 900 psig, a liquid hourly space velocity (LHSV) of1.0, and a hydrogen recycle of 150 to 200 SCF/Bbl. After hydrotreatingthe sulfur content was seen to have been reduced and color was improvedwhile pour point remained the same. The properties of the streams fromthe hydrotreater are shown in the following table:

    ______________________________________                                                   Ppm        D 1500     Pour                                         Stream     Sulfur     Color      Point of                                     ______________________________________                                        2           96        0.75       +12                                          3          225        1.25       +42                                          4          393        1.50       +70                                          5          503        2.25       +88                                          6          626        2.75       +94                                          ______________________________________                                    

The above hydrotreated streams were then catalytically dewaxed using acommercially available mordenite catalyst in hydrogen from (NortonZeolon H) to which had been added 0.5% by weight of platinum. Thedewaxing was carried out in a fixed bed trickle flow reactor operated at550° to 600° F., a hydrogen pressure of 850 psig, liquid hourly spacevelocity of 0.8 to 1.0 and a hydrogen recycle of 5000 to 9000 SCF/Bbl.The following table shows the yields of naphthenic-type lubricating oilproducts obtained and their pour points.

    ______________________________________                                        Yield, Wt. % of Charge   Product                                              Stream  C.sub.1 -C.sub.5                                                                        C.sub.5 -IBP                                                                            IBP    Pour Pt. °F.                        ______________________________________                                        2       3.5       4.5       92.0   -60                                        3       2.0       2.0       96.0   -40                                        4       5.0       3.0       92.0   -30                                        5       2.5       3.0       94.5   +08                                        6       1.5       0.5       98.0    70                                        ______________________________________                                    

As can be seen from the above table, Streams 2 to 5 yield a productfully meeting the specifications for naphthenic type lubricating oils.With extremely heavy grades such as stream 6 where the SUS/100° F.viscosity is 5000, the product obtained exceeds the pour pointspecification for the naphthenic type lubricating oils and such heavygrades from the vacuum distillation or optional hydrogenation step,rather than be subjected to catalytic dewaxing, would be used in otherrefinery operations or could be dewaxed by solvent dewaxing.

The invention claimed is:
 1. A process for making naphthenic typelubricating oils from a low VI waxy crude .Iadd.unsuitable for solventlubes .Iaddend.which consists of distilling said low VI waxy crude to500° to 650° F. at atmospheric pressure to separate distillablefractions therefrom, subjecting .Iadd.all of .Iaddend.the residue to avacuum distillation at about 25 to about 125 mm Hg absolute pressure toobtain one or more distillate fractions having an SUS at 100° F.viscosity of from about 60 to about 2000, and catalytically dewaxing.[.all of.]. said .[.distillates.]. .Iadd.distillate fractions.Iaddend.in the presence of an H⁺ form mordenite catalyst containing aGroup VI or Group VIII metal at 550° to 750° F., 500 to 1500 psig and0.25 to 5.0 LHSV to obtain said naphthenic type oils having a pour pointof from about -50° to +20° F.
 2. The process of claim 1 where the low VIwaxy crude is Nigerian Medium.
 3. The process of claim 1 where catalyticdewaxing is carried out in a fixed bed, trickle flow reactor.
 4. Theprocess of claim 1 where sulfur is added to the H⁺ mordenite catalyst.5. A process for making naphthenic type lubricating oils .[.fom.]..Iadd.from .Iaddend.a VI waxy crude which consists of atmosphericallydistilling said crude to remove wet gas, straight run gasoline, naphthaand atmospheric gas oil fractions, subjecting the residue to a vacuumdistillation at about 25 to 120 mm mercury pressure absolute to obtaingas oil fractions having an SUS at 100° F. viscosity of from about 60 toabout 2000, hydrotreating said gas oil fractions in the presence of aNi/Mo catalyst at about 650° F., a hydrogen pressure of about 800 psigand a LHSV of about 1.0, and catalytically dewaxing said hydrotreatedgas oil fractions in the presence of an H⁺ form mordenite catalystcontaining platinum at a temperature of about 550° to about 600° F., ahydrogen pressure of about 850 psig, and a LHSV of from about 0.8 toabout 1.0 to obtain naphthenic type oils having a pour point of fromabout -60° to about 20° F.
 6. The process of claim 5 where the low VIwaxy crude is Nigerian Medium.